According to the invention hereof, there is provided a compensation method and its apparatus for wavelength shift in Wavelength Selective Switch (hereinafter referred to as WSS). This invention is categorized into the photo-communication.
The development of wavelength division system and higher demand on its flexibility have facilitated the popularization of WSS, which can enable adding or dropping the wavelength arbitrarily at a random port and render a necessary technological platform for the flexible networking of optical networks.
WSS is often disseminated at different nodes of optical networks, thereby being required for reliable working at a large temperature range. Glass elements are often chosen for optical elements in WSS, which will be subjected to thermal expansion effect, leading to the change in their optical property. Besides, the glue through which the aforementioned optical elements and optical baseplate are connected is also under the thermal expansion effect, which might lead to the migration of optical elements. All this will cause the deviation of wavelength from the original direction, affecting ITU-T wavelength alignment in WSS, which will result in wavelength shift.
Capella Company put forward a compensation method for WSS wavelength shift through MEMS micromirror or LC array in its American patent application US2009/0028503A1 (publication date of Jan. 29, 2009). The patent claims to dispose the light path deflection element MEMS micromirror or LC array behind the collimator array to deflect light path. However, this method requires inserting the light path deflection element into the original light path, in which case the possible MEMS encapsulation is complex whilst LC array installation increasing difficulty in temperature controlling, polarization element disposing at the light path, the consequent light path optical alignment, and size expanding for whole apparatus.
JDSU Company came up with a compensation method for WSS wavelength shift through mechanical structure design and assembly method in its American patent application U.S. Pat. No. 8,036,502B2 (publication date of Dec. 22, 2009). The patent claims to adopt special design of optical baseplate and matching buffers, fixed buffer ensuring alignment position invariance between light line and MEMS chip, while moving buffer decreasing thermal stress caused by mismatching expansion coefficient between optical baseplate and optical shell and compensating for related wavelength shift. However, this method is not suitable for active compensation for wavelength shift and asks for a high standard for module encapsulation consistency.